This invention relates generally to radar detection, identification, and warning systems, and more particularly to a system and method for automatically determining radar scan type.
Many radar systems search, or scan, a spatial region to detect and track targets of interest. Typically, radar systems transmit energy at a specific transmission frequency (carrier frequency) or set of transmission frequencies. Detected frequency, time, and amplitude characteristics of radar signals are typically used to identify the type of transmitter used to transmit the received signals. Often inferred from these characteristics are the type of weapon system associated with the transmitter, and the present operational mode (e.g., search, track, missile-in-flight). Present techniques used to classify and identify the received radar signals rely primarily on the measured carrier frequency parameters, frequency modulation type parameters, and time domain modulation parameters such as pulse width and pulse repetition interval, and scan type, often inferred from the more easily determined scan period.
However, many radar types that perform the same functions, such as search or fire control, have parameter domains that overlap. Scan type is an important parameter for resolving these ambiguities, and for determining the mode of an associated weapons system. The scan type indicates the type of scanning technique being used by a radar system, for example, conical scan or circular scan. Historically, scan type could only be determined by a human operator (usually present on large or dedicated signal collection platforms, but rarely present on combat platforms, and never on weapons or remotely piloted vehicles), listening to the scan modulation. Typically, the operator would listen for several scan periods, and even then the analysis was subject to human interpretation. This analysis requires an experienced operator, whose actions and analyses are of course, subject to human error. The likelihood of such errors or mistakes may be further increased when the operator must perform in the heat of battle or under other crisis conditions. Current automatic classification systems only infer likely scan type or types from scan rate. Scan rate is the rate at which the transmitted radar pulse is received by the receiving radar system. The analysis performed by these systems is often ambiguous and, because the identification of scan type is inferred from measured scan period, the inference itself can be wrong. Therefore, there is a need for a fast, repeatable, highly accurate mechanism for the automated determination of scan type as an aid to identifying radar types and modes, that does not suffer the above disadvantages.
Energy received at an unintended receiver (the target or a collection system, at a location other than the transmitter""s receiver), also includes the signal amplitude envelope, modulated in accordance with the type of scan used by the transmitting radar system. Knowledge of the scan type can aid an operator (e.g., a pilot of a targeted aircraft, or an electronics warfare operator) in determining the type of radar transmission system, such as, for example ground base radar, airborne radar, or missile radar, and the mode of the associated weapons system (search, acquisition, track, missile guidance).
A system and method for determining a scan type of a signal include a scan detector for receiving a signal and providing an envelope signal. The envelope signal is indicative of the scan type of the signal. The envelope signal is transformed. A correlator compares the transformed envelope signal with at least one predetermined data set, wherein each predetermined data set corresponds to one of a plurality of scan types. The scan type of the signal is determined by a decision block in accordance with a degree of similarity between each of the predetermined data sets and the transformed envelope signal.